U.S. Pat. No. 4,474,539 discloses a dual pressure gas compressor having two gas compressors and a two-compartment tank. A first one of the gas compressors provides pressurized gas of a first (low) pressure to a first compartment of the tank, while the other one of the gas compressors provides pressurized gas of a second (higher) pressure to a second compartment of the tank. A conduit connects the first compartment of the tank to the input of the second compressor. Both compressors are operated by a single motor.
U.S. Patent Application Publication No. 2010/0913054 discloses a portable compressor having a permanently mounted first tank and a second tank that can be removed from the remainder of the portable compressor.
There remains a need in the art for a multi-pressure gas compressor having simultaneous running and charging systems.